This invention relates generally to devices for lifting objects. More particularly, this invention is directed towards crane hooks used to lift heavy objects in a manufacturing setting.
Devices such as cranes and other overhead hoists are common in industrial and manufacturing plants. Such devices are used primarily for lifting and manipulating heavy objects from a first position to a second position in a manufacturing facility or on a construction site.
Some crane devices, commonly referred to as bridge cranes, are positioned on rails suspended over a manufacturing plant floor. The hoisting device moves back and forth along a bridge that spans the rails, and the bridge itself is able to move forward and backwards along the rails. Such cranes are usually equipped to lift extremely heavy objects and move such objects within the generally rectangular area defined by the suspended crane rails and the bridge traversing the crane rails. Often, such overhead cranes are used to move objects back and forth, repetitiously, from one station in the manufacturing process to a second station located within the area serviced by the overhead crane.
Most overhead cranes or other hoists have a hooking element that can be raised or lowered as needed. The hooking element is normally positioned over the object to be transported and is then lowered to an appropriate level for attachment to the object. The hooking element and the attached object are then raised and moved from the first position to the second position in the manufacturing facility. Often, the hooking element is attached to the crane in such a manner as to minimize twisting of the object while it is being lifted. For example, the hooking element may be attached at the end of a cable and pulley system, or reeve, which acts to resist the twisting forces that naturally act on an object as it is lifted from the ground. While an object may initially and naturally turn slightly from its initial position as it is lifted from the ground, the reeving system will apply resistance to cause the object on the hooking element to return to its initial, fixed position. The more stable configuration of the hooking element improves the ability of the crane operator to control the object being lifted.
Often times, it is desired to rotate or manipulate the object in a controlled fashion as the object proceeds between the various stations in the manufacturing process. It will be appreciated that this can usually be most efficiently accomplished while the object is suspended, between its point of departure and its destination. When controlled rotation of the object is desired, it is usually necessary to equip the overhead crane with special machinery to achieve the required rotation of the hooking element. The current practice used to rotate heavy objects to a specific orientation often involves powered mechanized equipment installed on or near the point of attachment of the hooking element to the crane cables, sometimes referred to as the rotating hook block, which is also proximate to the point of attachment to the object being transported. However, these motorized devices, which have moving parts, require frequent maintenance and are often not ideal for handling certain objects such as those that radiate intense heat such as open-top ladles containing molten iron or steel. The extremely high temperatures emitted from the molten metal can cause maintenance and reliability problems for the machinery that is attached to the crane and used to rotate the object.
Alternatively, the object can be manually manipulated using rigging devices such as slings or chains. However, manual manipulation is time consuming and makes the manufacturing process less efficient. In addition, manual manipulation can subject the operators to safety risks. For example, the intense heat of certain objects being lifted and manipulated poses safety concerns to those who would be exposed to the heat while rotating the object. There is, as a result, a need for a device that can accomplish the controlled rotation of objects being lifted, particularly objects of extremely high temperatures.
As suggested by the foregoing discussion, an exemplary and non-exclusive alternative object of this invention is to permit a remote crane operator to lift an object such as a container of molten metal or other potentially hazardous load in one orientation and to rotate the object to a different, predetermined orientation without manual intervention or the use of powered mechanized equipment. Although the device will have common application with all types of cranes, it is expected that the device can be used in various other lifting applications.
The above objects and advantages are neither exhaustive nor individually critical to the spirit and practice of the invention. Other or alternative objects and advantages of the present invention will become apparent to those skilled in the art from the following description of the invention.